Cu-al catalyst for hydrogenation

ABSTRACT

A process for hydrogenating bound oxygen-containing organic feeds into their corresponding alcohols by contact with a coprecipitated copper-aluminum catalyst that has been activated by contact with reducing gas at a temperature that gradually increases.

FIELD OF THE INVENTION

The invention relates to a process for the catalytic vapor phasehydrogenation of bound oxygen-containing organic compounds andparticularly to the catalytic hydrogenation of esters.

DESCRIPTION OF RELATED TECHNOLOGY

The hydrogenation of, for example, mono-esters normally yields alcoholsaccording to a simple relationship:

    RC(O)OR'+2H.sub.2 →R'OH+RCH.sub.2 OH

The hydrogenation of diesters generally results in a more complicatedproduct mixture. For example, the hydrogenation of a dialkyl maleatetypically results in the formation of several products, the amount ofeach depending on the reaction conditions:

    ROC(O)CH═CHC(O)OR+xH.sub.2 →2ROH+1,4-Butanediol+Tetrahydrofuran+gamma-Butyrolactone

The concentrations of each of the products are a function of theequilibrium reaction conditions, e.g. temperature, pressure, liquidhourly space velocity (LHSV), and gas hourly space velocity (GHSV) ofthe process. Like most hydrogenation reactions, the processes areusually catalyzed and are affected strongly by the composition of thecatalyst used in the process. Typical hydrogenation catalysts for estersare a combination of reduced copper and zinc (GB 2,150,560 and WO83/03409) or reduced copper-chromite (U.S. Pat. Nos. 2,100,483;3,767,595; and 4,584,419). Various promoters can be added as disclosedin U.S. Pat. No. 2,109,844 (barium or cadmium).

U.S. Pat. Nos. 2,297,769; 4,209,424; 4,593,015; and 4,600,704 and EP0143,634 discuss particular reduction activation processes--forcopper-based catalysts.

In EP 143,634 the vapor phase hydrogenation of diethyl maleate isreported. The hydrogenation reaction is carried out with acopper-chromite catalyst at 170°-190° C. and approximately 450 psig. Itis disclosed that controlled reduction of the catalyst is necessary toensure high catalyst activity. The reduction process involves a rapidheating directly to a reduction temperature of and maintaining thattemperature more or less constant over the entire reduction period.

SUMMARY OF THE INVENTION

It is an objective of the invention to provide an activated,copper-based catalyst for the hydrogenation of bound oxygen-containingorganic compounds.

It is another objective to provide a process that results in an active,selective catalyst and a hydrogenation process using such a catalyst.Other objectives will become apparent from the description containedherein.

In accordance with the invention, the invention comprises an activehydrogenation catalyst composition produced by reducing a homogenousmixture of copper and aluminum oxides by heating in the presence of areducing gas under activation conditions which comprise reductiontemperature that gradually increases from a starting temperature ofabout 40° to 75° C. to a final temperature of about 150° C. to 250° C.The resulting catalyst is useful for catalyzing the vapor phasehydrogenation of bound oxygen-containing organic compounds, in general,and esters, in particular to produce various hydrogenated products suchas alcohols. For example, the catalyst of the present invention can beused to hydrogenate diethyl maleate to produce a hydrogenated productcontaining inter alia, such desired products as ethanol,tetrahydrofuran, 1,4-butanediol and gamma-butyrolactone.

The process according to the invention produces catalysts that providehigh rates of conversion with control over the distribution of products.

DETAILED DESCRIPTION OF THE INVENTION

The catalyst of the invention, which is useful in the inventive process,is an activated combination of copper and aluminum. The weight ratio ofCu:Al in the catalyst can vary widely. Active catalysts may have aweight ratio of Cu:Al of about 90:10 to about 10:90 when calculated asthe elemental forms of each. More preferably, the catalyst has a weightratio of copper to aluminum of between about 75:25 to about 25:75.

The catalyst is made by the controlled reduction of a catalyst precursorcontaining a more or less homogeneous mixture of the oxides of copperand aluminum. The catalyst precursor can be made by coprecipitatingcopper and aluminum from any of their water soluble salts in the desiredweight ratio and/or by mixing finely divided oxides of copper andaluminum. Coprecipitation is preferred. Suitable water soluble saltsinclude, inter alia, the chlorides, sulfates, lactates and nitrates ofcopper and aluminum. Preferred are the nitrate salts of each component.Coprecipitation of copper and aluminum can be induced by adding anaqueous solution of sodium carbonate to the solution of the copper andaluminum salts. The precipitated salts are washed, dried to a slightlyelevated temperature, e.g., about 80° C. to about 120° C., and calcinedin air, e.g., at 350°-450° C. for 1 to 3 hours to yield homogenous oxidecatalyst precursors.

Catalyst precursors are transformed into catalysts according to theinvention by heating the calcined mixture of copper and aluminum in areducing atmosphere at a gradually increasing temperature, typicallyfrom an initial temperature of between about 40° to 75° C. to a finalreduction temperature of between about 150° to 250° C., preferablybetween about 160° C. and 220° C., and most preferably from an initialtemperature of about 50° C. to a final temperature of about 180° C. Thetemperature is gradually increased, normally by increasing thetemperature of the reducing atmosphere, at a positive rate of normallyless than about 24° C./hr (0.4° C./min), preferably at a rate of about3°-18° C./hr (about 0.05°-0.3° C./min.), and most preferably at a rateof about 3°-6° C./hr (0.05°-0.1° C./min). The heating rate andconditions normally are chosen to produce a catalyst composition havinga high activity to maximize hydrogenation efficiency, e.g., theformation of alcohols. However, in certain instances, as may beencountered when hydrogenating diesters, such as dialkyl maleates, itmay be desired to optimize the reduction conditions to produce acatalyst that favors one or more hydrogenation product relative toothers. For example, in the case of hydrogenating diethyl maleate,reduction conditions may be selected to provide a catalyst that favorsthe production of tetrahydrofuran, or gamma-butyrolactone relative toethanol or 1,4-butanediol.

The heating rate should be chosen to minimize or avoid the generation ofan exothermic temperature rise which can result during the reduction ofCu-Al catalysts. See, U.S. Pat. Nos. 2,297,769; 4,209,424; 4,593,015;and 4,600,704 all of which are incorporated herein by reference.

The reduction process according to the invention can be monitored toavoid an exotherm by comparing the rate of actual temperature rise inthe catalyst bed to the temperature increase rate that would occur inthe absence of any exothermic reduction as a consequence of the heatingrate applied with external means, e.g. heated reducing gas, resistanceheaters around and/or throughout the catalyst bed, etc.

If desired, a variable rate of temperature increase, obtained forexample by combining different temperature increase rates within theranges identified above, also can be used to produce a catalystaccording to the invention, e.g., the precursor can be reduced byinitially increasing the temperature at a rate of 0.06° C./hr for 2hours followed by a further reduction at a temperature which increasesat the rate of about 0.5° C./hr for 3 hours, etc.

Exemplary reducing gases include hydrogen, carbon monoxide, and mixturesthereof in addition to other reducing gases known to those in this art.The reducing gas can be supplied a pressure of about 1-20 atm. and maybe supplied in admixture with an inert gas. If an inert gas is used, thereducing gas to inert gas volumetric ratio can be about 0.1:20 to about10:1. Suitable inert gases include, inter alia, nitrogen, argon, andmethane. The GHSV in the reduction step can be within the range of about100 to about 100,000 per hour.

The length of the reduction period depends upon the initial reductiontemperature, the final reduction temperature, and the rate oftemperature increase. Generally, reduction (activation) of the precursorcatalyst is done over a period of about 12 to 48 hours. The resultingcatalyst is useful for catalyzing the hydrogenation of boundoxygen-containing organic compounds and particularly esters to produce avariety of hydrogenated products, particularly alcohols.

A variety of organic feeds containing bound oxygen may be hydrogenatedusing the reduced copper-aluminum catalysts of the invention. Suitablefeeds include: (1) aromatic and nonaromatic (aliphatic and alicycliccarboxylic acids having more than one carbon atom per carboxyl group),esters of monobasic acids exemplified by acetic, propionic, butyric,caprylic, lauric, capric, myristic, palmitic, linoleic, oleic,ricinoleic, stearic, hexahydrobenzoic and hexahydrotoluic acids; (2)esters of nonaromatic, dibasic and polybasic acids exemplified byhexahydrophthalic, azelaic, sebacic, succinic, suberic, pimelic,nonanedicarboxylic, decamethylenedicarboxylic, brassylic, and adipicacids, dodecamethylenedicarboxylic, and hexadecamethylenedicarboxylicacids; (3) esters of hydroxy, aldehydic, and ketonic acids, e.g. lactic,ricinoleic, tartaric, and pyruvic acids; (4) mixtures of esters such asthose listed above or obtained as a result of the saponification of afat such as coconut oil; (5) esters of hydroaromatic acids; (6) mono-and dialkyl oxalates; (7) mono-esters, di-esters, and mixtures thereof;and (8) straight or branched chain, saturated or unsaturated aldehydescontaining from 2 to about 22 carbon atoms.

The general formula for mono-esters that can be hydrogenated accordingto the invention is R¹ C(O)OR² where R¹ and R² may be the same ordifferent and represent aliphatic groups having from 1 to 22 or morecarbon atoms. Exemplary mono-esters are methyl acetate, butyl acetate,and methyl propionate. Suitable di-esters have the general formula R³OC(O)R⁴ C(O)OR⁵. R³ and R⁵ have the same definitions as for R¹ and R²above. R⁴ is the bridge between the two ester groups and can be asaturated or unsaturated hydrocarbon moiety having from 1 to 10 or morecarbon atoms. Exemplary di-esters that can be hydrogenated according tothe invention include esters having up to about 16 or more carbon atomsof primary or secondary alcohols, e.g. dialkyl maleates and dialkylsuccinates. Mono-esters and di-esters may be hydrogenated individuallyor in combination.

As noted above, the catalyst of the present invention can also be usedfor hydrogenating a wide variety of straight or branched chain,saturated or unsaturated aldehydes containing from 2 to 22 carbon atoms.The range of useful feed stocks is limited only by the practicality ofvaporizing the higher boiling aldehydes. Any technique that can vaporizethe aldehyde is useful for extending the range of feed stocks forhydrogenation with the catalysts according to the invention. Suitablealdehydes include saturated aldehydes like acetaldehyde,propionaldehyde, iso-butyraldehyde, n-butyraldehyde, isopentyl aldehyde,2-methylpentaldehyde, 2-ethylhexaldehyde, 2-ethylbutyraldehyde,n-valeraldehyde, iso-valeraldehyde, caproaldehyde, iso-hexaldehyde,caprylaldehyde, n-nonylaldehyde, n-decanal, dodecanal, tridecanal,myristic aldehyde, pentadecaldehyde, palmitic aldehyde, stearic aldehydeand such unsaturated aldehydes as acrolein, methacrolein, ethacrolein,2-ethyl-3-propylacrolein, crotonaldehyde and the like. The aldehyde maybe in a substantially pure state or mixed with a component or componentsother than the aldehyde itself. Furthermore, a mixture of aldehydes maybe employed.

The aldehyde or mixture of aldehydes employed may be obtained by an oxoprocess. Either a portion or all of the product mixture of an oxoprocess, i.e., the reaction of olefins with carbon monoxide and hydrogenin the presence of a catalyst to add a carbonyl group at one of thecarbon atoms of the olefinic group, can be used. Of course, the aldehydeor mixture of aldehydes can be obtained by processes other than the oxoprocess such as by oxidation of olefins or saturated hydrocarbons or byan aldol condensation. The present invention is not limited to thesource of any particular aldehyde or other bound oxygen-containingcompound.

In accordance with the process of the present invention, the boundoxygen-containing, organic compound feed in a vaporous state is broughtinto contact with the hydrogenation catalyst in the presence of areducing gas, e.g., hydrogen-containing gas. Although substantially purehydrogen can be used, it is preferable in some cases to provide thehydrogen to the reaction in admixture with other gases, desirably inertto the feed and catalyst. Suitable inert gases for mixing with hydrogenare nitrogen, methane, and argon. The term "hydrogen-containing gas"includes both substantially pure hydrogen gas as well as gaseousmixtures containing hydrogen.

While the concentration of hydrogen in the reaction zone is notcritical, generally there should be an excess of hydrogen over thestoichiometric requirement relative to the organic feed to behydrogenated. The mole ratio of hydrogen to organic feed will usually befrom about 5 to about 400 and preferably from about 10 to 200.

The process of the present invention preferably is carried out in acontinuous manner. In the preferred method of continuous operation, theorganic feed or the mixture of organic feeds are vaporized as needed andbrought together with the hydrogen-containing gas at the desiredtemperature and pressure in the presence of the catalyst of the presentinvention.

An inert diluent, such as an aliphatic hydrocarbon, may be fed into thehydrogenation reactor along with the organic feed being hydrogenated.Alkanes such as pentane or hexane are examples of suitable diluents. Thevolumetric ratio of organic feed, e.g., ester, to diluent may vary withthe reactor system but can typically be within about 0.5 to about 4.Other ratios may be used both above and below this range.

The catalyst advantageously may be used in a fixed, fluidized,ebullating, or moving catalyst bed reactor. Preferably, a fixed bed isused in an elongated tubular reactor having the catalyst supportedwithin the tubes. Adiabatic tank type reactors also can be used. In suchreactors, the heat of reaction causes an increase in reactiontemperature from reactor inlet to reactor outlet.

The hydrogenation may be effected at a temperature of about 100°-300°C., at a pressure of about 200-2000 psig, about 0.1-10/hr LHSV, andabout 1,000-50,000/hr GHSV. Preferably, the reaction is conducted at atemperature of 120°-260° C., at a pressure of less than about 600 psig,and about 0.1-4/hr LHSV. In view of the need to maintain the organicreactant feeds and reaction products (typically alcohols) in thevaporous state and above their dew points, the chosen reaction pressureis influenced somewhat by the reaction temperature, the nature of theorganic feed undergoing hydrogenation and the quantity ofhydrogen-containing gas. Optimizing these factors to operate the processin the vapor phase is within the ordinary skill level existing in thisart. The hydrogenation may be effected in one or more stages.

As used herein, LHSV refers to the volumetric feed rate of the organicfeed component passed to the catalyst bed as a liquid divided by theunit volume of catalyst of the bed. In a parallel definition, GHSVrefers to the volumetric feed rate of all gas or vapor components fed tothe catalyst bed at standard temperature and pressure divided by theunit volume of the catalyst bed.

Appropriate organic feeds and processing sequences for use with theinvention are set forth in U.S. Pat. Nos. 4,172,961; 4,032,458;2,079,414; 4,112,245; 4,584,419; and 4,762,817 the disclosures of whichare herein incorporated by reference.

The following examples are presented to illustrate the invention: theexamples are not intended to limit the scope of the invention as setforth in the appended claims.

EXAMPLES Preparation of Catalyst Precursors

An active hydrogenation catalyst according to the invention is made byfirst preparing a precursor catalyst composition. The catalyst precursorthen is subject to an activation (reduction) treatment under carefullycontrolled conditions in accordance with the present invention.

A precursor catalyst can be prepared by dissolving copper nitrate andaluminum nitrate in deionized water at 25° C. The solution of metalsalts and a separate solution of sodium carbonate are individuallyheated to about 45°-75° C. The carbonate solution is quickly added tothe nitrate solution with rapid stirring to produce a precipitate. Theprecipitated mixture is stirred while cooling to 25° C. The precipitateis isolated, washed with deionized water, dried in air at a slightlyelevated temperature, e.g. about 80° C. to about 120° C., and thencalcined in air at about 300° to about 550° C. The resulting materialwhich comprises the hydrogenation catalyst precursor is pressed intopellets and crushed into particles of about 30-40 mesh. It is to beunderstood that the drying step may be combined with the calcinationstep if desired.

For example, a Cu(54):Al(46) catalyst precursor may be prepared in thefollowing manner. A first solution (Solution A) is prepared bydissolving Cu(NO₃)₂.3H₂ O (10.2 g) and Al(NO₃)₃.9H₂ O (39.22 g) in 200mL deionized water (25° C.). A second solution (Solution B) is preparedby dissolving Na₂ CO₃ (30 g) in 100 mL deionized water (25° C.).Solutions A and B are heated to 60° C. Solution B is then quickly addedwith rapid stirring to Solution A resulting in formation of aprecipitate. This mixture is stirred for 3 hr. while cooling to 25° C.The precipitate is isolated and washed with 1000 mL of deionized water(25° C.). The precipitate then is dried in the air at 100° C. for 18 hrand calcined in air at 400° C. for 2 hr. The resulting material whichconstitutes the catalyst precursor can be pressed into pellets andcrushed into particles in the 30/40 mesh range. Other compositions canbe made similarly.

The hydrogenation catalyst precursors used in the following exampleswere made using substantially the same process by simply changing therelative amounts of the various ingredients.

Reduction and Hydrogenation Procedures

The precursor catalysts made in this manner then are reduced inaccordance with the present invention. Unless otherwise stated in theexamples which follow, the following standard process conditions wereused to activate the precursor catalysts. Under these conditions 0.5 or1 cc of (unreduced) precursor catalyst is loaded into the rear third ofa stainless steel reaction tube. The reaction tube is a U-tube designwhere the first two-thirds of the tube is packed with inert glass beads.This front section serves as a gas and liquid preheater. The precursorcatalyst is activated in situ with a mixture of 0.5% hydrogen innitrogen at a standard GHSV of 1800/hr, at an initial temperature ofabout 50° C. with the temperature gradually increased at a rate ofbetween 0.05° C./min (3° C./hr) to 0.1° C./min (6° C./hr) to a finaltemperature of about 180° C. in an oven equipped to handle four reactiontubes.

Once activated, the gas flow is switched to pure hydrogen, and thepressure and flow rate are adjusted to the desired hydrogenationconditions. Unless otherwise stated in the following examples, thefollowing standard hydrogenation conditions were used. The liquid feedrate of the ester together with hexane as a diluent is adjusted to aLHSV of 0.6/hr. The diluent ratio is typically 1:1 by volume for theexamples. Due to the preheater section, the ester feed is vaporized andcontacts the catalyst as a vapor.

The standard hydrogenation reaction conditions are set at a temperatureof 220° C., at a pressure of 450 psig and at a GHSV of 15,000/hr atwhich they are maintained for 20 hours. During the last 4 hours, thehydrogenation products are collected by passing the reactor effluentthrough a series of condensation traps containing isopropanol andmaintained at 0° to -75° C. The products are analyzed with a capillarygas chromatograph using a 30 mm×0.32 mm capillary. The products in theexamples are reported in terms of weight percent and exclude anyisopropanol or inert diluent.

Table 1, and succeeding tables associated with the subsequent examples,report the weight percent of various components in the hydrogenatedproduct stream including ethanol (EtOH), tetrahydrofuran (THF), butanol(BuOH), gamma-butyrolactone (g-BL), 1,4-butanediol (BD) and diethylsuccinate (DES). The level of DES in the hydrogenation product providesan indication of catalyst activity. Lower levels of DES in thehydrogenation product indicate higher hydrogenation activities for thecatalysts.

EXAMPLES 1-8

These examples demonstrate that the method used to activate a catalystcan have a marked impact on catalyst performance. The catalysts wereobtained by activating precursor catalysts both according to theinvention and according to the procedure outlined in EP 143,634 for acopper-chromite catalyst. In Examples 1-3 and 5-7, the precursorcatalysts were heated at a low, constant rate of heating to cause thecatalyst temperature to increase gradually over the range 50°-180° C. inthe presence of a reducing atmosphere of 1% H₂ in N₂. Examples 4 and 8illustrate the EP procedure where the precursor catalyst is rapidlyheated (10 min) to a temperature of 150° C. under an atmosphere of 0.5%H₂ /N₂ and maintained at 150° C. for 22 hr. The listed time is the timerequired to traverse the 50°-180° C. temperature range at the given heatrate.

Table 1 presents the results of hydrogenating diethylmaleate at standardconditions illustrating the effects of varying the catalyst heat rateduring activation (reduction) on catalyst performance. The weight ratioof the catalyst elements is shown in parentheses.

                                      TABLE 1                                     __________________________________________________________________________    Various Reduction Procecures                                                              Heat.sup.1                                                                            Products                                                  Example                                                                            Catalyst                                                                             Rate                                                                              Time.sup.2                                                                        EtOH                                                                              THF                                                                              g-BL                                                                             BD DES                                          __________________________________________________________________________    1    Cu(70):Al(30)                                                                        0.3  7.2                                                                              28.2                                                                              25.8                                                                             8.2                                                                              0.2                                                                              34.9                                         2    Cu(70):Al(30)                                                                        0.1 21.6                                                                              36.0                                                                              36.1                                                                             7.4                                                                              0.0                                                                              18.8                                         3    Cu(70):Al(30)                                                                         0.05                                                                             43.3                                                                              52.8                                                                              1.5                                                                              29.4                                                                             11.0                                                                             2.6                                          4    Cu(70):Al(30)                                                                        EP  --  31.9                                                                              30.9                                                                             7.1                                                                              0.8                                                                              27.7                                         5    Cu(54):Al(46)                                                                        0.3  7.2                                                                              38.3                                                                              1.5                                                                              26.6                                                                             9.8                                                                              22.3                                         6    Cu(54):Al(46)                                                                        0.1 21.6                                                                              53.3                                                                              2.6                                                                              29.1                                                                             11.5                                                                             0.5                                          7    Cu(54):Al(46)                                                                         0.05                                                                             43.3                                                                              50.1                                                                              34.6                                                                             3.3                                                                              0.1                                                                              7.7                                          8    Cu(54):Al(46)                                                                        EP  --  47.7                                                                              1.8                                                                              32.4                                                                             11.4                                                                             4.5                                          __________________________________________________________________________     .sup.1 °C./min over the range 50°-180° C. EP             reduction procedure: the catalyst is heated in 10 min to 150° C.       and maintained at 150° C. for 22 hrs.                                  .sup.2 Time in hours to traverse 50°-180° C.               

Table 1 illustrates the effects of heating rate on the catalyst activityand selectivity relative to the constant-temperature reduction processof EP 143,634. The Cu(70):Al(30) catalyst did not exhibit its bestactivity at the same heating rate as the Cu(54):Al(46) catalyst. Basedon the amount of undesirable DES in the product mixture, the mostdesirable catalysts of Examples 3 and 6 according to the invention havea more desirable product mixture than the catalysts of examples 4 and 8.

EXAMPLES 9 to 11

These examples illustrate the effect of varying the H₂ /N₂ GHSV whilemaintaining a constant reduction heating rate.

The catalyst precursors were reduced at a heating rate of 0.1° C./minbetween 50° and 180° C. while varying the GHSV of the reduction gas (1%H₂ in N₂) from 600 to 5400 hr⁻¹. The activated catalysts were screenedusing diethylmaleate as the ester feed at standard hydrogenationconditions. The results are reported in Table 2.

It is theorized that if left uncontrolled, the exothermic heat of thereduction reaction can drive the reaction forward too quickly andadversely affect the subsequent performance of the reduced catalyst. Theevolution of heat is thought to act according to the followingrelationship.

    CuO+H.sub.2 →Cu°+H.sub.2 O+Heat

                                      TABLE 2                                     __________________________________________________________________________    Effect of Reduction Gas GHSV on Catalyst Activity                                              Heat                                                                             Products.sup.2                                            Example                                                                            Catalyst                                                                             GHSV.sup.1                                                                         Rate                                                                             EtOH                                                                              THF                                                                              g-BL                                                                             BD DES                                          __________________________________________________________________________     9   Cu(54):Al(46)                                                                         600 0.1                                                                              46.5                                                                              1.7                                                                              29.9                                                                             17.4                                                                             3.3                                          10   Cu(54):Al(46)                                                                        1800 0.1                                                                              53.3                                                                              3.6                                                                              29.1                                                                             11.5                                                                             0.5                                          11   Cu(54):Al(46)                                                                        5400 0.1                                                                              61.8                                                                              3.1                                                                              23.6                                                                             7.9                                                                              1.1                                          __________________________________________________________________________     .sup.1 H.sub.2 /N.sub.2 space velocity during reduction (hr.sup.-1)           .sup.2 All hydrogenation runs: GHSV = 15000/hr                                Temperature = 220° C.                                                  Pressure = 450 psi                                                       

From Table 2, the flow rate of the gas used in the reduction stepappears to have an effect on the activity level of the resultingcatalyst. The preferred combination of reduction gas flow rate andheating rate for activating a particular precursor catalyst can bedetermined by one skilled in this art with no more than routineexperimentation.

Comparative Examples 1-4

Nonhomogeneous Cu-Al catalysts were prepared by impregnating alumina(Al₂ O₃) with various amounts of copper. In comparative Examples 1, 3,and 4, the heterogeneous catalysts were made by impregnating Al₂ O₃ withan aqueous solution of copper nitrate. In comparative Example 2, thecatalyst was prepared by the well-known incipient wetness technique.These comparative catalysts were reduced at a temperature that wasgradually increased over the range of 50°-180° C. at a rate of 0.1°C./min. Diethyl maleate was hydrogenated in the presence of the reduced,nonhomogeneous catalysts under the standard conditions of 220° C., 450psig, and GHSV of 15,000/hr. Results are shown in Table 3.

                  TABLE 3                                                         ______________________________________                                        Compara-                                                                      tive    Catalyst Products                                                     Example (Cu:Al)  EtOH    THF  BuOH  g-BL BD   DES                             ______________________________________                                        1       25:75    6.2     0.8  0.1   4.8  0.0  87.1                            2       25:75    1.1     0.0  0.0   0.0  0.0  98.5                            3       50:50    19.6    3.6  0.1   11.2 0.4  64.3                            4       70:30    51.2    1.2  0.8   23.0 18.4 4.8                             ______________________________________                                    

In general, non-homogeneous catalysts prepared by supporting copper onalumina are inferior to the homogeneous Cu-Al catalysts (e.g. preparedby co-precipitation) because they result in a product mixture high inundesirable DES and low in desired 1,4-butanediol, gamma-butyrolacone,or THF.

EXAMPLES 12-16

Cu-Al catalysts prepared in accordance with the present invention wereutilized in the hydrogenation of dibutylmaleate (DBM). The catalystswere prepared by co-precipitation and activated under a graduallyincreasing temperature over the temperature range of 50°-180° C. at arate of 0.1° C./min for Examples 12 and 14 and a rate of 0.05° C./minfor Examples 13, 15, and 16. The hydrogenation reactions were carriedout at the standard conditions of 220° C., 450 psig, and a GHSV of15,000/hr. The results are reported in Table 4.

                  TABLE 4                                                         ______________________________________                                        Ex-                                                                           am-            LHSV/                                                          ple  Catalyst   hr.     THF  BuOH  g-BL BD   DBM                              ______________________________________                                        12   Cu(44):Al(56)                                                                            0.3     1.2  70.4  21.6 5.5  0.0                              13   Cu(44):Al(56)                                                                            0.6     1.2  76.6  17.9 2.5  0.0                              14   Cu(44):Al(56)                                                                            1.2     0.4  69.1  19.0 6.7  3.9                              15   Cu(54):Al(46)                                                                            1.2     1.5  69.8  21.2 6.0  0.1                              16   Cu(70):Al(30)                                                                            1.2     24.4 63.5  5.8  0.1  3.3                              ______________________________________                                         KEY: DBM = unreacted dibutyl maleate.                                    

EXAMPLES 17-18

Hydrogenation of butyl acetate (BuOAc) was carried out. The desiredproducts are ethanol and n-butanol according to the following reaction:

    CH.sub.3 C(O)OCH.sub.2 CH.sub.2 CH.sub.2 CH.sub.3 +H.sub.2 →CH.sub.3 CH.sub.2 OH+CH.sub.3 CH.sub.2 CH.sub.2 CH.sub.2 OH

The results are reported below in Table 5. The precursor catalysts werereduced using the standard conditions. The hydrogenating reactions wererun at the standard hydrogenating conditions of 220° C., 450 psig and aGHSV of 15,000/hr.

                  TABLE 5                                                         ______________________________________                                                                Products                                              Exam-                   (wt %)                                                ple   Catalyst   LHSV (hr.sup.-1)                                                                         EtOH  BuOH  BuOAc                                 ______________________________________                                        17    Cu(44):Al(56)                                                                            0.6        35.1  63.4  0.06                                  18    Cu(44):Al(56)                                                                            1.2        32.3  63.1  0.5                                   ______________________________________                                         BuOAc = Unreacted butyl acetate                                          

These results demonstrate that mono-esters are readily hydrogenated withCu-Al catalysts of the present invention.

EXAMPLES 19-22

Cu-Al catalyst precursors of various compositions were preparedaccording to the above-described procedure. The precursor catalysts werereduced over the temperature range 50°-180° C. at the heat rate shown inTable 6 below. Hydrogenation of diethyl maleate was carried out usingthe standard hydrogenation conditions. The results are reported below inTable 6.

                                      TABLE 6                                     __________________________________________________________________________                    Products                                                                  Heat                                                                              (wt. %)                                                       Example                                                                            Catalyst                                                                             Rate.sup.(1)                                                                      ETOH                                                                              THF                                                                              BuOH                                                                              g-BL                                                                             1,4-BD                                                                            DES                                         __________________________________________________________________________    19   Cu(28)Al(72)                                                                         0.05                                                                              28.9                                                                              12.0                                                                             0.1 11.0                                                                             0.3 42.0                                        20   Cu(44)Al(56)                                                                         0.1 43.8                                                                              29.5                                                                             0.2 6.3                                                                              0.1 17.7                                        21   Cu(54)Al(46)                                                                         0.1 56.6                                                                              2.2                                                                              0.7 21.9                                                                             17.2                                                                              0.2                                         22   Cu(70)Al(30)                                                                         0.05                                                                              50.1                                                                              34.6                                                                             0.2 3.3                                                                              0.1 7.7                                         __________________________________________________________________________     .sup.(1) C/min                                                           

EXAMPLES 23-24

A Cu(46)Al(56) catalyst prepared and activated using the standardprocedures was examined for its performance when hydrogenating diethylmaleate using the standard hydrogenation conditions except that the LHSVwas varied between 0.3/hr and 0.5/hr. The results are reported below inTable 7.

                                      TABLE 7                                     __________________________________________________________________________                     Products                                                                      Approximate Weight Percent                                   Example                                                                            Catalyst                                                                              LHSV.sup.(1)                                                                       ETOH                                                                              THF                                                                              BuOH                                                                              g-BL                                                                             BD DES                                        __________________________________________________________________________    23   Cu(44)Al(56)                                                                          0.3  53.9                                                                              43.0                                                                             0.6 0.0                                                                              0.0                                                                              0.0                                        24   Cu(44)Al(56)                                                                          0.5  54.1                                                                              40.9                                                                             0.3 0.8                                                                              0.0                                                                              0.3                                        __________________________________________________________________________     .sup.(1) hr.sup.-1                                                       

EXAMPLES 25-29

The Cu(54)Al(46) catalyst of the above examples (23 and 24) was examinedfurther at various hydrogenation operating conditions. The results arepresented below in Table 8.

                                      TABLE 8                                     __________________________________________________________________________                     Products                                                                      (wt. %)                                                      Example                                                                            LHSV.sup.(1)                                                                       temp.sup.(2)                                                                      psi                                                                              GHSV.sup.(1)                                                                       ETOH                                                                              THF                                                                              BuOH                                                                              g-BL                                                                             BD DES                                    __________________________________________________________________________    25   0.3  220 450                                                                              15000                                                                              45.9                                                                              3.3                                                                              0.8 19.8                                                                             29.1                                                                             0.1                                    26   0.6  220 450                                                                              10000                                                                              61.1                                                                              2.4                                                                              0.5 27.7                                                                             7.4                                                                              0.3                                    27   0.6  220 450                                                                              20000                                                                              47.6                                                                              1.3                                                                              0.4 26.6                                                                             20.6                                                                             2.9                                    28   0.6  220 600                                                                              15000                                                                              62.4                                                                              2.5                                                                              0.6 20.6                                                                             12.8                                                                             0.3                                    29   0.6  250 450                                                                              15000                                                                              52.7                                                                              5.1                                                                              3.8 27.9                                                                             9.1                                                                              0.0                                    __________________________________________________________________________     .sup.(1) hr.sup.-1                                                            .sup.(2) °C.                                                      

While certain specific embodiments of the invention have been describedwith particularity herein, it will be recognized that variousmodifications thereof will occur to those skilled in the art, and it isto be understood that such modifications and variations are to beincluded within the purview of this application and the spirit and scopeof the appended claims.

We claim:
 1. A reduced catalyst composition consisting of copper andaluminum made by a process comprising:coprecipitating copper andaluminum from their water soluble salts to form a precipitate; dryingand calcining the precipitate to form a calcined catalyst; andactivating the calcined catalyst by heating said calcined catalyst inthe presence of a reducing gas under activation conditions whichcomprise a reducing temperature that gradually increases from an initialtemperature of about 50° C. to a final temperature of about 180° C. andwherein said reducing temperature is gradually increased at a rate ofabout 3° C. to about 6° C. per hour.